Polishing the hull-technique

[FairweatherDave]

I bought the Silverline 1200w polisher following threads here but having used it for a few hours I confess physically I have struggled, and my results are not that great. I'm not a gorilla but like to think I'm reasonably strong 50 something...

Basic question. I believe you are supposed to hold the pad very lightly flat against the hull. Often, with slightly too much pressure the polisher would shoot off in a random direction. This seemed to be reduced if I introduced a slight angle, say 5 to 10 degrees. Was I doing it right? Very occasionally I got control with it pretty much flat.RPM was set to approx 1500-2000

For those not familiar with the machine it has a 180mm diameter backing pad and uses a hook and loop system. I was using a hook and loop lambs wool bonnet. In retrospect I would have got better results with a more aggressive compound and a second go round with a wax, but the truth is that will do for this year. But my question is about technique. I probably did both sides of my 29ft hull in five hours. So probably did not put enough time and effort in.

Lastly... Is a lambs wool bonnet suitable for what I did...... if not what would you use?
PS I did you a little water spray occasionally which did help with control a bit

 

[pvb]

I've always done it by hand. If you choose appropriate products, it can be fairly easy and give good results.

 

[FairweatherDave]

I know! I think your hull is in better condition than mine.
http://www.ybw.com/forums/showthread.php?378455-Compunding-and-polishing-help
Somehow studying this thread before polishing the boat and I still haven't resolved my basic questions.......

 

[Fr J Hackett]

Tie a piece of strong bungee cord to it and the toe rail or stantion which will take the weight of it and allow you to work it up and down and across gradually moving the bungee as you work down the hull. You do need to apply some pressure and the above technique will help.

 

[pvb]

I know! I think your hull is in better condition than mine.
http://www.ybw.com/forums/showthread.php?378455-Compunding-and-polishing-help
Somehow studying this thread before polishing the boat and I still haven't resolved my basic questions.......

Well, it was a 20+ year old hull, which had seen a lot of use in the Med and in the UK. My view is that amateur use of power tools can cause gelcoat damage. Better to proceed carefully by hand, it's very difficult to do serious harm that way.

 

[VicS]

I bought the Silverline 1200w polisher following threads here but having used it for a few hours I confess physically I have struggled, and my results are not that great. I'm not a gorilla but like to think I'm reasonably strong 50 something...

Basic question. I believe you are supposed to hold the pad very lightly flat against the hull. Often, with slightly too much pressure the polisher would shoot off in a random direction. This seemed to be reduced if I introduced a slight angle, say 5 to 10 degrees. Was I doing it right? Very occasionally I got control with it pretty much flat.RPM was set to approx 1500-2000

For those not familiar with the machine it has a 180mm diameter backing pad and uses a hook and loop system. I was using a hook and loop lambs wool bonnet. In retrospect I would have got better results with a more aggressive compound and a second go round with a wax, but the truth is that will do for this year. But my question is about technique. I probably did both sides of my 29ft hull in five hours. So probably did not put enough time and effort in.

Lastly... Is a lambs wool bonnet suitable for what I did...... if not what would you use?
PS I did you a little water spray occasionally which did help with control a bit

I have one of the Silverline sander/ polishers I have always used a foam compounding mop and one of the appropriate paste rubbing compounds. ( Farecla, Starbrite etc) I keep the speed down pretty low and keep every thing moist with water in a trigger spray bottle. It can get messy so sometimes have had to cover the next boat.

I usually apply the final wax polish and buff up by hand.

It is hard work if you are not used to it. I have usually taken 2 days to compound a 19 footer, working on about a square metre at a time. Both sides of a 29 footer in 5 hours ... no way, not even when I was under 50.

If I was starting out again these days I would probably use one of the newer "self- lubricating" liquid compounds and a lambswool bonnet but I am not at all likely to do it again.

 

[paulajayne]

"keep every thing moist with water in a trigger spray bottle"

^^^^^^^

This plus bungee from toe rail.

 

[pcatterall]

Just done my 33 footer by hand using T cut. Good wash with detergent first then Heavy pressure and about 12 inches square per day of liquid, wipe off the removed gelcoat when just dry. Then 3 coats of a good wax polish buffing between coats. About 6 hours per side. Hard work as you do need pressure to cut through the oxidised surface.
I'm past my sell by date now so you young whippersnappers should do it in no time!

 

[savageseadog]

Do about 4 sq ft at a time. Keep it moist initially with a spray bottle, I use a larger pump up garden spray with a lance. Buff with a dab of compound until it almost dries and get the shine on the last few swirls of the mop. It's not too bad, I can do a 38 footer in a day.

 

[gjgm]

Lots over on mobo chat and youtube.
Personally..you need to spend a bit of money I am afraid.
Bin the mop that came with it.
Try either a 3m bonnet that also needs a backing plate, or a double mop..afraid that is 35 to 50 quid.
For an old hull you will need to restore the surface and for that you will first need a compound paste..again try 3M. After that you need to use a polish such as 3M finnesse it 2....then you need to wax...sorry..but I am going to suggest 3M again..the wax is by hand but very easy.
The polisher can be used at a very shallow angle if needed and ensure the gelcoat doesnt start getting too bot. To be honest..you would need to be making a right pig of things for that to happen..just keep the polisher moving.
Oy work in front of your shoulders..and about a 50 cm area. Please do not stretch or tie the polisher to anything. Speed about 2.
It IS a big job...

 

[Concerto]

Fairweather Dave

I have used a Silverline polisher to compound and then polish the tired gel coat on my Westerly Fulmar. You have a Westerly, so firstly you should know they applied a double layer of gel coat. This will be about 3mm thick when moulded. Some thinning over time will have occurred, but you have plenty to cut the top layer off to reveal the original colour. Westerly boats moulded in the late 1970's and early 1980's used a Ryland gel coat that was not UV stable so has gone cream colour over time.

If the hull is discoloured then I suggest you hand wet sand the hull with 400 grade, followed by reducing finer grades until you reach 1000 grade (but you could try skipping these). Then start with your Silverline with a course compound, then a fine compound for a high shine (I use G3 and G10 https://www.farecla.com/product_groups/classic/) using a foam pad with lots of water from a plant spray. Then finally use the lambswool pad with your polish.

This photo shows the dividing line before and after just using the Farecula G3.



This how she looked after polishing and new painted style.

 

[Poignard]

Nice work, Concerto. :encouragement:

 

[FairweatherDave]

Thanks all. Interestingly diverse replies on how long it should take. Next year I will try and make it higher priority.
Only one person refered to my bit about the angle of attack. I would be interested still on opinions there about very slight tilt versus completely flat.

 

[Marine Reflections]

Thanks all. Interestingly diverse replies on how long it should take. Next year I will try and make it higher priority.
Only one person refered to my bit about the angle of attack. I would be interested still on opinions there about very slight tilt versus completely flat.

It takes as long as it takes to get from current condition to your desired state. To a large degree, this can vary between boats and also between the different surface angles on the same boat.


The angle of attack:

Again lots of variables, choice of the pad, polish, machine, current surface condition and your working height/position.

The most important IMHO is the surface being ready to be polished.
Think of it like trying to polish a bed of nails with a lambswool polisher. The nails will grip the pad and a fight will follow.
The nails are the highs of a rough surface, they may only be 1000th of a mm, but they will make work very difficult indeed.

For this reason, 'flatting' a surface before polishing/correction works well.

Now assuming you have a surface that is less like a bed of nails, the ultimate position to reduce swirl marks and ghost tails is to have the pad flat against the surface.

You won't be able to achieve this at all times, and a slight angle can be introduced to adjust the rotational forces pushing or pulling you in another direction.

If you were polishing a sheet of glass on a bench, you'd probably be able to determine a flat position of the pad and stick with it. With so many angles on a boat and with many positions you physically need to get into to make life easy on the back, staying with one angle of attack is not possible all the time.
That said, nearly all of the time you should be able to polish an area with a flat pad even if it's just for an ending pass. This will reduce many swirls and make further clarity easier in the next stages.

The trick is to provide an opposing force and use the rotation to your advantage.
To avoid muscle fatigue you might want to switch muscle sets, be pulling instead of pushing, only to switch 2 minutes later.

The pad being 360º and rotating in a clockwise fashion, slight pressure or tilt at 12 o'clock or 6 o'clock will provide different directional pulls. Flat to the surface you should be able to hold it with one hand as it is balanced. (note: If the surface is a bed of nails, don't try this)
With a slight tilt, you will be providing more pressure on one section of the rotation, this will fight more, but will correct faster, recovery on next stage will be harder.


Then you have the physical position you need to be in to be working that section, the closer to the surface you are working the easier it will be, as opposed to having both arms out-stretched like a zombie, get in tight. If working with the surface below you then get a good wide base in the upper body.
Adjust and shift positions often; the pain will soon make the default choices for you.
If standing and polishing a head height surface, people have said it looks like I'm slow dancing with the polisher, this is exactly how it should feel, lead the polisher and let it work for you.

To add: I've said this an awful lot... tying anything to a rotational mechanism that has extreme torque is not the best idea despite it appearing so. It'll end in tears...It is not the weight of the machine that is causing the problem; it is the rotation.

 

[FairweatherDave]

Wow. Brilliant.Thanks for taking the time to write that. It makes good sense. Allowing enough time for the job and getting the right pads etc etc ..... Maybe using a bit of a platform so that you are holding the machine at a comfortable height.

 

[Marine Reflections]

Wow. Brilliant.Thanks for taking the time to write that. It makes good sense. Allowing enough time for the job and getting the right pads etc etc ..... Maybe using a bit of a platform so that you are holding the machine at a comfortable height.

Yes, a platform helps, it's an essential piece of kit. Surprised yards don't hire them out.

Just a note about allowing enough time, instead work a section 2ft x 2ft to the best possible reflection. The feedback should enable you to work more efficiently on the whole.

 

[johnalison]

I agree that a platform is essential for hull work. I bought one from Homebase that fits in my A3 hatchback for about £120 but I expect there are better or cheaper ones around. It was one of the best additions to my kit and halves the time spent.

On my HR, the white hull only needs cleaning and waxing. I use a gelcoat cleaner from a squeegee mop on a pole and wash it off with a pad on a pole. The whole boat only takes about 20 mins. The blue line is now getting tired, so I use a cutting compound buffed with a lambswool pad on a rotary drill held at an angle and moistened. I follow this with the slightly abrasive Starbrite colour-restorer polish buffed by hand, then wax and sealer as for the white bits. For my 34 it takes three gentle days work.

 

[Concerto]

Nice work, Concerto. :encouragement:

Thank you. The topsides took about 2 days to compound in those photographs. However I have since then compounded them twice as I could still see some feint yellowing. This picture was taken in June last year and the topsides are nearly perfect. By comparison you can see the sides of the coach roof are creamy and need a lot more work. The repeated compounding would have been avoided if I had sanded the topsides first.



Just to show how creamy the gel coat in the cockpit had gone, this photo shows where the gel coat has been sanded.



The comments about a staging are correct, you do need one. In the first photo of my last post shows the one I used from Machine Mart. https://www.machinemart.co.uk/p/clarke-sl-2c-4-way-combination-ladder/

Hope my comments are of help to Fairweather Dave and others.

 

[shaunksb]

Lots over on mobo chat and youtube.
Personally..you need to spend a bit of money I am afraid.
Bin the mop that came with it.
Try either a 3m bonnet that also needs a backing plate, or a double mop..afraid that is 35 to 50 quid.
For an old hull you will need to restore the surface and for that you will first need a compound paste..again try 3M. After that you need to use a polish such as 3M finnesse it 2....then you need to wax...sorry..but I am going to suggest 3M again..the wax is by hand but very easy.
The polisher can be used at a very shallow angle if needed and ensure the gelcoat doesnt start getting too bot. To be honest..you would need to be making a right pig of things for that to happen..just keep the polisher moving.
Oy work in front of your shoulders..and about a 50 cm area. Please do not stretch or tie the polisher to anything. Speed about 2.
It IS a big job...

I’ve just ordered a silver line with a “cheap” optional 115mm pad which I thought might make it easier working in smaller areas. Is there a foam mop that’s ok but not quite as expensive as the 3m stuff or do I have to bite the bullet.

And where would I get one from?

____________________________________

 

[Daydream believer]

I think that 1500 rpm is too fast. I have a dedicated Draper polisher with variable speed & run it much slower. the comments about using the rotation to your advantage are valid. If you angle the pad so that the rotation is lifting the polisher rather than forcing it downwards it will ease muscle strain. However, some polishes can be applied by hand just as easily & provided one works from a tower with the work at chest height the job is far easier.